The present application claims the benefit of and priority to a provisional patent application entitled “Light Sensor with Chemically Resistant and Robust Reflector Stack,” Ser. No. 62/045,706 filed on Sep. 4, 2014. The disclosure in this provisional application is hereby incorporated fully by reference into the present application.
Light sensors, such as infrared sensors, can operate on the principle that electrical resistance of an absorbing layer changes in response to radiation reflected from a reflector underlying the absorbing layer. For example, when the absorbing layer gets heated by radiation reflected from the reflector, a change in electrical resistance can be detected by a readout integrated circuit. The sensitivity of the light sensor may depend on many factors, such as the planarity of the reflector. For example, a substantially flat reflector surface can greatly improve a signal to noise ratio to ensure the sensitivity of the light sensor.
Since the reflector of the light sensor is an underlying layer below the absorbing layer, the reflector is formed, for example, on a substrate before other features of the light sensor are formed. As a result, the reflector is subject to harsh chemical and temperature environments during downstream processing actions, such as polishing, high power asking, and etching. Thus, the reflective properties of the reflector in the light sensor can be greatly impacted by these downstream processing actions, resulting in a decreased sensitivity of the light sensor.
Thus, there is a need in the art for robust and chemically resistant reflector structures to enhance structural and functional performance and stabilities of the light sensors.